The Solar System - Textbook PDF

FOR ONLINE USE ONLY DO NOT DUPLICATE Chapter Eleven The solar system Introduction When you were in Standard Four, you learnt about the solar system. You learnt about the eight planets in the solar system and th...

FOR ONLINE USE ONLY DO NOT DUPLICATE Chapter Eleven The solar system Introduction When you were in Standard Four, you learnt about the solar system. You learnt about the eight planets in the solar system and the features found on earth. You LY also learnt about the difference between sunlight and moonlight. In this chapter, you will learn more about the solar system, the earth, earth movements and their results. N The solar system O The solar system is the arrangement of the sun, moon and planets which revolve around the sun. The sun is a star and it is closer to the earth than SE the other stars. Since the sun is close to the earth, its light is more intense than that of the other stars. The sun is at the centre of the solar system and all planets revolve around it. U In the solar system there are eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Each planet revolves around the sun E in its elliptical path called an orbit. The time taken for a planet to revolve around the sun depends on the distance between the sun and that planet. N For example, Mercury completes its revolution around the sun in 88 days, while the earth revolves around the sun for 365 ¼ or 366 days. Each planet LI in the solar system has different characteristics. N The earth O The earth is one of the planets which make up the solar system. In studying the solar system, we have seen that the planets are in a special arrangement. R The earth is the third in the arrangement of the planets from the sun. The earth has several characteristics. It is the only planet where all living things FO are found. Also, three quarters of the earth is covered by water. It also has oxygen and carbon dioxide which are important to living things. Moreover, the earth receives light from the sun. 127 SOCIAL STUDIES STD 5.indd 127 30/07/2021 11:49  FOR ONLINE USE ONLY Exercise 1 DO NOT DUPLICATE Answer the following questions: 1. What is the solar system? 2. What is an orbit? 3. Why do planets take different times to revolve around the sun? 4. Mention eight planets which make up the solar system. LY 5. Mention four characteristics of the earth. Movements of the earth N The earth has two movements. The first movement is known as rotation. This movement involves the spinning of the earth on its axis (refer to Figure O 1). The second movement is known as revolution. This movement involves the earth revolving around the sun. These two movements occur at the same SE time. The earth rotates from West to East. It completes one rotation on its axis in 24 hours or 1 day. The earth revolves around the sun for 365 ¼ or 366 days, which are equal to one year. U NORTH POLE E N THE EARTH’S AXIS LI Wes tto Ea st N O R FO SOUTH POLE Figure 1: The earth rotating on its axis 128 SOCIAL STUDIES STD 5.indd 128 30/07/2021 11:49  FOR ONLINE USE ONLY DO NOT DUPLICATE Results of the earth’s rotation When the earth rotates on its axis, we get day and night, the rising and falling of tides, as well as change in the direction of winds and ocean currents. Also, we get differences in time between one longitude and another. The earth takes four minutes to rotate from one degree of longitude to another; therefore, it uses 60 minutes, which is equal to one hour, to rotate 15 degrees of longitude. Thus, the difference in time between each 15 degrees of longitude is one hour. Oceanic tides LY These involve a steady rise and fall of the levels of ocean water. In some coastal areas, there are times when water moves away from the shore and N times when water moves closer to the shore. Such movements are called low and high tides. When water moves away from the shore, it is known as a O low tide and when it returns to the shore, it is known as a high tide. Causes of the rise and fall of oceanic tides SE The rise and fall of oceanic tides occurs because of the changes caused by gravitational force between the earth and the moon. This force causes the U rise and fall of the level of water in an ocean, and thus produce the tides. The part of the earth which is facing the moon at that moment is the one that is mostly affected by the force of attraction; water piles up and causes a high E tide. The moon’s attraction causes water to be drawn from the side which is not facing the moon at that moment and causes a low tide. The moon N causes two high tides and two low tides in 24 hours or in one day. LI Effects of the daily rise and fall of oceanic tides N When sea water makes high and low tides, it can have the following results: O (a) Soil erosion on sea shores, especially when there are large waves; (b) Low and high tides bring certain sea products onto the shore. The R products include corals, shells of sea snails, shallow shells and small cowry shells. These sea products are used by people for decoration FO and other purposes. Figures 2 and 3 show some of the sea products. 129 SOCIAL STUDIES STD 5.indd 129 30/07/2021 11:49  FOR ONLINE USE ONLY DO NOT DUPLICATE LY N O Figure 2: Sea products on the shore SE U E Figure 3: Examples of sea shells N Results of the earth’s revolution LI When the earth is revolving around the sun, we get four seasons of the year: summer, winter, autumn and spring. Also, we get differences in length N between night and day for a certain period of the year. For example, the sun sets very late in the period from November to January but sets early in O the period from June to July. In its revolution, the earth is closest to the sun on 3rd January each year. This period is known as Perihelion. On 6th July R each year, the earth is farthest from the sun. This period is called Aphelion (Figure 4). Also, when the earth is revolving around the sun, we get different FO dimensions of the overhead sun in different periods of the year. Moreover, when the earth is revolving around the sun, it causes solar and lunar eclipses. 130 SOCIAL STUDIES STD 5.indd 130 30/07/2021 11:49  FOR ONLINE USE ONLY DO NOT DUPLICATE v v Aphelion Perihelion 152.0 million km 147.3 million km LY v v N O Figure 4: The earth revolving around the sun Activity 1 D SE  iscuss with your classmates the different seasons of the year and then mention the months which are hot, rainy, dry and cool in your region. U Exercise 2 E Answer the following questions: N Write True for a true statement and False for a false statement. LI 1. The earth has two movements. ________ N 2. When the earth is revolving around the sun, we get day and night. ________ O 3. Day and night have the same length throughout the year. ________ R 4. When the earth is revolving around the sun, we get the seasons of the year. ________ FO 131 SOCIAL STUDIES STD 5.indd 131 30/07/2021 11:49  FOR ONLINE USE ONLY Exercise 3 DO NOT DUPLICATE Choose the letter with the most correct answer: 1. Which of the following is the correct duration of the earth’s revolution? (a) 24 hours (b) 365 ¼ or 366 days ( ) (c) Day and night (d) 300 days LY 2. How long does the earth take to rotate between one longitude and another? N (a) 15 minutes O (b) 24 minutes ( ) (c) (d) 4 minutes 60 minutes SE 3. How often do changes of low and high tides happen? U (a) Every day E (b) Per week ( ) N (c) Per year (d) After one month LI 4. Which of the following planets support life? N (a) Saturn O (b) Neptune ( ) R (c) Venus (d) Earth FO 132 SOCIAL STUDIES STD 5.indd 132 30/07/2021 11:49  FOR ONLINE USE ONLY DO NOT Put a tick (ü) in the brackets for a DUPLICATE correct statement and an (×) for an incorrect statement. 5. The earth rotates around the sun. ( ) 6. The earth takes 24 hours to rotate on its axis. ( ) 7. The earth takes 365 ¼ days to revolve around the sun. ( ) 8. The earth takes 24 hours to revolve around the sun. ( ) LY 9. Day and night occur because the sun rotates around the earth. ( ) Write True for a true statement and False for a false statement. N 10. The revolution of the earth on its axis produces day and night. O _______ 11. SE Some of the products found on sea shores are shells and cowry shells. _______ 12. The difference in time for every 15 degrees of longitude is one hour. U _______ 13. Low and high tides happen because of the gravitational force of E attraction between the moon and the sun. _______ N 14. The earth rotates on its axis from East to West. _______ LI N Vocabulary O Aphelion the period of the year when the earth is farthest from the sun R Autumn  the season of the year, which comes after summer, FO when leaves fall from trees and the weather is colder 133 SOCIAL STUDIES STD 5.indd 133 30/07/2021 11:49  FOR ONLINE USE ONLY Gravitational force theDO NOT force of DUPLICATE attraction between all masses in the universe, for example the attraction between the moon and the earth Orbit  a curved path followed by a planet as it revolves around the sun Perihelion the period of the year when the earth is closest to the sun Spring the season of the year between winter and summer LY during which temperature rises gradually Summer the warmest season of the year N Winter the coldest season of the year O SE U E N LI N O R FO 134 SOCIAL STUDIES STD 5.indd 134 30/07/2021 11:49